Connecting element and joint

ABSTRACT

The invention relates to a connecting element ( 7 ) and a joint for joining pieces of wood. The connecting element is adapted to be placed between two pieces of wood to be joined and comprises a body ( 8 ) with two opposite main surfaces and with engaging means ( 9 ) which protrude from each main surface. In addition, the joint comprises a connecting means ( 10 ) which is adapted to be passed through the pieces of wood and the connecting element ( 7 ) and apply a compressing force on the pieces of wood in such a manner that the engaging means ( 9 ) of the intermediate connecting element penetrate into opposite wood surfaces. The connecting element ( 7 ) comprises a through hole perpendicular to the main surface for passing through the shank-shaped connecting means ( 10 ). The hole exhibits engaging formations round its circumference, and the connecting means ( 10 ) exhibits matching engaging formations ( 15 ) on its shank part in such a manner that longitudinal displacement is allowed while rotary motion of the connecting means relative to the connecting element is prevented.

[0001] The present invention relates to a connecting element for joiningpieces of wood, comprising a body with two opposite main surfaces andwith engaging means which protrude from each main surface, and thepurpose of which, when placing the connecting element between two piecesof wood to be joined, is to penetrate into opposite wood surfaces andconnect the pieces of wood with one another.

BACKGROUND ART

[0002] So-called nail plates are well known within the technique ofjoining different pieces of wood to one another. Such nail plates areusually made of a metal sheet which has a thickness of a few millimetresand in which flanges have been punched, which have been folded outwardsso that they protrude from one main surface of the plate. The nailplates are used for joining in nodal points, where different pieces ofwood meet in the same plane. In such joints, the main purpose is toabsorb tensile stress in the longitudinal direction of the pieces ofwood, and nail plates are well suited for this purpose.

[0003] It is already known from GB 2 322 425 that a joint and a palletwhere two pallet elements not located in the same plane are connectedsurface against surface by a combination of a nail plate between thepallet elements and nails which are completely driven through at leastone of the pallet elements, penetrate through the nail plate and adistance into the other pallet element. The purpose of the nail plate isin this case only to increase the shearing strength relative to acorresponding joint using only nails and not actually to connect thepallet elements with one another. However, in the same patentspecification an alternative embodiment is disclosed where thepunched-out flanges are folded outwards in opposite directions so thatthe flanges protrude from the two main surfaces of the plate. Whenplacing such a nail plate between two pieces of wood, the nail plate, ofcourse, also has a certain uniting effect on the pieces of wood, but thenail plate is in this case combined with through-nailing through boththe nail plate and the pieces of wood. A common feature of all nailplates in this patent specification is that flanges are punched out fromonly certain portions of the plates, while others are left unperforatedand reserved for the through nails. Such combined joints with nails aswell as nail plates most likely obtain sufficient strength. However, itis time-consuming to produce them and once the pallet, or some otherproduct that is connected in the same manner, is to be either discardedor mended, it is extremely difficult to dismantle them. When discarding,the parts included should as a rule for environmental reasons be dividedinto wood material for burning and metal for recycling, and it may bedifficult to make this separation with a reasonable time expendituresince nails and nail plates can be wedged very tightly in one another.When mending and replacing separate parts of a pallet, it may for thesame reasons be difficult to separate the parts without also breakingthe parts that are to be kept. Naturally, also the total perforation ofthe pieces of wood on the one hand by conventional nails and, on theother, by the spikes of the nail plates increases the risk of the woodmaterial already cracking during the joining.

BRIEF SUMMARY OF THE INVENTION

[0004] An object of the present invention is to eliminate thedisadvantages of prior-art wood joints of the type mentioned by way ofintroduction and create a connecting element which allows easy and fastconnection of two pieces of wood located in different planes withespecially great shearing strength and torsional strength, and easy andquick dismounting of the pieces of wood with the purpose of discardingor mending. At least these objects are achieved by means of a connectingelement as claimed in claim 1.

[0005] The invention also relates to a joint mainly having the sameobjects as mentioned above. These objects are achieved by means of ajoint as claimed in claim 4.

[0006] The invention is thus based on the understanding that anefficient and appropriate connecting element is obtained by forming ontwo opposite main surfaces of the element protruding engaging means andforming, in a through hole perpendicular to the main surfaces, for ashank-shaped connecting means, engaging formations in the form of, forexample, grooves, ridges or projections. By means of such a connectingelement, an efficient and appropriate joint is obtained by placing theelement between two wood surfaces which are to be connected, and bypassing through a shank-shaped connecting means which exhibits engagingformations matching the engaging formations of the connecting element,which allows longitudinal displacement but prevents rotary motion of theconnecting element relative to the connecting means. The purpose of theshank-shaped connecting means is to pull the pieces of wood towards oneanother in such a manner that the protruding engaging means of theintermediate connecting element penetrate into the opposite woodsurfaces, and can, for example, be a bolt having a screw-threaded nutand grooves formed on the shank of the bolt. However, the shank-shapedconnecting means can be of the type shown in SE 511 140, which isparticularly suited to easily and dismountably join pallets. In thefollowing detailed description of a preferred embodiment of theinvention, the connecting element and a joint according to the inventionare shown and described by using a connecting means according to saidpatent specification.

[0007] By placing a connecting element according to the inventionbetween two pieces of wood and with the aid of a shank-shaped connectingmeans applying a force that presses the pieces of wood together, theprotruding engaging means on the respective main surfaces of theconnecting element will penetrate into the corresponding wood surfacesand give improved torsional strength between the pieces of wood. Byforming the hole in the connecting element and the shark of theconnecting means with engaging formations matching one another andallowing longitudinal displacement of the connecting means through thehole but preventing rotation between the same, the rotation-preventingaction is further improved. Various combinations of engaging formationsare possible within the scope of the invention, for instance, ridges orprojections on the shank of the connecting means in combination withgrooves or recesses in the hole of the connecting element. The oppositeis also conceivable, i.e. longitudinal grooves in the shank of theconnecting element and ridges or projections in the hole of theconnecting element.

[0008] The invention is applicable in all joints where two or morepieces of wood are to be joined surface against surface in differentplanes. The received manner so far when it comes to providing arotation-preventing action between the pieces of wood in such a joint isto join the pieces of wood with at least two but, if possible, moreconnecting means in the form of, for example, nails, screws, bolts andthe like which are arranged at a distance from one another across asurface as large as possible. However, this is time-consuming andincreases the risk of cracking in the wood. By means of the presentinvention, it is thus possible to provide an excellentrotation-preventing action using only one connecting means in eachjoint. The advantages of this are many. For example, only one hole needsto be drilled and both mounting and dismounting are easily and quicklycarried out.

[0009] According to a preferred embodiment, the connecting element andthe joint according to the invention are used when joining pallets inorder to provide pallets having high stability without any tendency ofgetting warped but being easy and quick to mount and dismount fordiscarding and/or replacing damaged parts.

[0010] In a preferred embodiment, the connecting element is made ofplastics, e.g. polypropylene, the protruding engaging means suitablybeing formed directly when injection moulding the element. However, itshould, of course, be possible to make the connecting element of metal,e.g. by punching out flanges in a plate, the flanges being bent outwardsto each side in order to form the engaging means. One advantage ofmaking the connecting element of plastics is that, when discarding woodproducts, such as pallets, the product can directly be chipped withoutany previous dismounting and removal of metal parts. The shank-shapedelement means according to said SE 511 140 is in a preferred embodimentalso made of plastics.

[0011] In a preferred embodiment, the connecting element is furtherformed as a thin plate with a circular outer shape. The body of theconnecting element is plate-shaped and has a thickness which essentiallyis smaller than its largest width and, in particular, the thickness isno more than 10%, preferably no more than 7% and most preferably no morethan 4% of the width. However, the invention is not limited to thisembodiment but could, for example, have a square or some other outershape. In addition, the connecting element does not need to be flat orthin but could have a considerable thickness. For example, in palletsthere are distance elements for joining a bottom deckboard and a crosspiece at a distance from one another. This distance element could beformed as a connecting element according to the present invention withprotruding engaging means on the respective main surfaces.

[0012] It should be understood that the term piece of wood comprises alltypes of wood-based construction material, such as homogeneous timber,laminate, wood particle boards, OSB boards, plywood, fibre boards andthe like. It would also be possible to join different plastic materialby means of a connecting element and a joint according to the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0013] In the drawings

[0014]FIG. 1 is a perspective view of a conventional pallet, in whichthe present invention is applicable for connecting its nodal points,

[0015]FIG. 2 is a cross-section through one of the nodal points in thepallet according to FIG. 1,

[0016]FIG. 3 is a cross-section along the line A-A in FIG. 4 of aconnecting element according to the invention, and

[0017]FIG. 4 is a top view of the connecting element in FIG. 3.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

[0018] First reference is made to FIG. 1 which shows a pallet ofpreviously known, conventional type. The pallet exhibits a loading deckin the form of parallel top deckboards 1, distance elements 2, a bottompart in the form of bottom deckboards 3, and cross pieces 4 which arepositioned between the top deckboards and the distance elements andextend perpendicular to the top deckboards and the bottom deckboards. Inthis embodiment, the pallet has fifteen nodal points where pieces ofwood in different planes are to be joined surface against surface. Thenodal points are of two types, on the one hand, nodal points 5 where topdeckboards 1, cross pieces 4, distance elements 2 and bottom deckboards3 are to be joined and, on the other, nodal points 6 where only topdeckboards 1 and cross pieces 4 are joined.

[0019] Subsequently, reference is made to FIG. 2 which shows across-section through a nodal point 5 according to FIG. 1, the nodalpoint being formed with a joint according to the present invention. Theparts which are included in the pallet are, counting from above, a topdeckboard 1, a cross piece 4, a distance element 2 and a bottomdeckboard 3. A connecting element 7 is positioned between the crosspiece 4 and the distance element 2 and between the distance element 2and the bottom deckboard 3, respectively. This is made with a body 8 inthe form of a plate or a sheet which on each main surface exhibitsprotruding engaging means 9.

[0020] In order to press the parts of the pallet together, which areincluded in the nodal point, a connecting means known from SE 521 540 isused in the shown embodiment and comprises, on the one hand, ashank-shaped female port 10 with a flanged portion or head 11 at its oneend and, on the other, a shank-shaped male part 12 which also is formedwith a flanged portion or head 13 at one of its ends and which isinsertable into a bore in the female part from its end which is notprovided with a head. The male part is engagable with the female partthrough grooves or flutes 14 on the shank of the male part which engagewith corresponding flutes in the bore of the female part. The outside ofthe shank of the female part is formed with a plurality of ridges 15extending in its axial direction.

[0021] When mounting, all parts included have to be pre-drilled so thatthe female part and male part of the connecting means can be insertedinto the pre-drilled hole from one direction each and, subsequently, themale part is pressed into the female part as far as possible, wherebyalso the parts included in the pallet will be pressed together and theprotruding engaging means 9 of the connecting elements 7 will penetrateinto the wood material on each side of the connecting element.

[0022] The pre-drilled hole should have a diameter corresponding to theshank of the female part but somewhat smaller than the maximum diameterbetween two opposite ridges 15. These will thus somewhat penetrate intothe wood material and give increased torsional rigidity.

[0023]FIG. 4 shows that the inner circumference of the hole through theconnecting element 7 is formed with a plurality of recesses 16, thediameter of the hole and the number, shape, size and position of therecesses corresponding to the diameter of the shank of the female partand the number, shape, size of the ridges 15 in such a manner that thefemale part can be longitudinally displaced through the connectingelement 7 but rotation is prevented by the ridges 15 and recesses 16engaging in one another. The torsional rigidity of the joint is thusfurther increased.

[0024]FIGS. 3 and 4 show that the connecting element 7 in the preferredembodiment is formed as a flat, thin, circular disc and the protrudingengaging means 9 are conically pointed and circular seen in planes. Asmentioned previously, the connecting element could, however, be designedin many different ways. In an alternative embodiment, the actualconnecting element could, for example, constitute distance elements in apallet of the type described above. The connecting element 7 would thushave the same thickness as the distance element 2 in FIGS. 1 and 2 withengaging means 9 protruding from each main surface thereof.

1. A connecting element for joining pieces of wood, comprising a body(8) with two opposite main surfaces and with engaging means (9) whichprotrude from each main surface, and the purpose of which, when placingthe connecting element (7) between two pieces of wood to be joined, isto penetrate into opposite wood surfaces and connect the pieces of woodwith one another comprising a through hole perpendicular to the mainsurfaces in order to allow a shank-shaped connecting means (10) to bepassed through the hole of the connecting element and the correspondinghole in the pieces of wood, the connecting element (7) around thecircumference of its hole exhibiting engaging formations (16) which areadapted to engage with matching engaging formations (15) on the shankpart of the connecting means in such a manner that longitudinaldisplacement is allowed while rotary motion of the connecting meansrelative to the connecting element is prevented.
 2. A connecting elementas claimed in claim 1, wherein the body (8) of the connecting element isplate-shaped and has a thickness that is essentially smaller that itslargest width and, the thickness is no more than 10%, of the width.
 3. Aconnecting element as claimed in claim 1 that is made of plastic.
 4. Ajoint for joining pieces of wood, comprising a connecting element (7)which is adapted to be positioned between two pieces of wood to beconnected and which exhibits a body (8) with two opposite main surfacesand with engaging means (9) protruding from each main surface, and ashank-shaped connecting means (10) which is adapted to be passed throughthe pieces of wood and the connecting element and apply a compressingforce on the pieces of wood in such a manner that the engaging means (9)of the intermediate connecting element penetrate into the opposite woodsurfaces, wherein the connecting element (7) comprises a through holeperpendicular to the main surfaces for passing through the shank-shapedconnecting means (10), the hole exhibiting engaging formations (16)around its circumference, and the connecting means exhibits matchingengaging formations (15) on its shank part in such a manner thatlongitudinal displacement is allowed while rotary motion of theconnecting means relative to the connecting element is prevented.
 5. Aconnecting element as claimed in claim 4, wherein the engagingformations (16) of the connecting element (7) have the shape of groovesor recesses while the engaging formations (15) of the connecting means(10) have the shape of ridges or projections.
 6. A connecting element asclaimed in claim 1, wherein the body (8) of the connecting element isplate-shaped and has a thickness that is essentially smaller than itslargest width and the thickness is no more than 7% of the width.
 7. Aconnecting element as claimed in claim 1, wherein the body (8) of theconnecting element is plate-shaped and has a thickness that isessentially smaller than its largest width and the thickness is not morethan 4% of the width.
 8. A connecting element as claimed in claim 2 thatis made of plastic.